The present invention generally relates to semiconductor manufacturing and, more particularly, to chemical-mechanical polishing (CMP) of metal films.
Chemical-mechanical polishing (CMP) removes material from the top layer of a substrate in the production of ultra-high density integrated circuits. Often, the top layer is a metal film, but other materials can also be removed. In a typical CMP process, the top layer is exposed to an abrasive medium under controlled chemical, pressure, velocity, and temperature conditions. Conventional abrasive media comprises slurry solutions and polishing pads. The slurry solution can be provided shortly before use by mixing a so-called precursor with an oxidizing agent. The precursor lacks the oxidizing agent, but comprise the other components of the slurry (e.g., abrasive media, catalysts, water).
It is required that material is removed only to a predetermined film thickness; any further removal must be prevented. Endpointing techniques are used to determine whether the desired thickness has been reached or not. The polishing ratexe2x80x94that means the decrease of film thickness with the timexe2x80x94is very crucial. When the polishing rate is too high, the endpoint is easily missed; when the polishing rate is too low, the overall CMP processing time becomes too long.
The present invention seeks to provide an improved method which mitigates or avoids disadvantages and limitations of the prior art.